1. Field of the Invention
The present invention relates to a fundus observation device, for observing the state of the fundus oculi of an eye to be examined.
2. Description of the Related Art
As a fundus observation device, conventionally a fundus camera has been widely used. FIG. 9 shows one example of the appearance of a conventional fundus camera in general, and FIG. 10 shows one example of an optical system composition to be internally accommodated therein (e.g. JP Patent laid-open No. 2004-350849). Furthermore, “observation” is intended to include at least a case in which produced fundus images are observed (fundus observations with the naked eye may be included).
First, referring to FIG. 9, an explanation is made regarding the appearance of a conventional fundus camera 1000. This fundus camera is provided with a platform 3 mounted on a base 2 slidably in the front and rear, right and left (horizontal direction) directions. On this platform 3, an operation panel 3a and a control lever 4 are installed for an examiner to conduct various operations.
The examiner may place the platform 3 on the base 2 to be moved 3-dimensionally by operating the control lever 4. On the top of the control lever 4, an operation button 4a is installed to be pressed down to form fundus oculi images.
On the base 2, a post 5 is installed standing upwards. On the post 5, a jaw rest 6 where the jaw of a patient is to be rested and an external fixation lamp 7 as a light source for fixing an eye to be examined E are provided.
On the platform 3, a main body part 8 is installed to accommodate various optical systems or control systems of the fundus camera 1000. Furthermore, the control system may be installed inside the base 2 or the platform, etc., or in an external device such as a computer, etc. connected to the fundus camera 1000.
On the side of the eye to be examined E of the main body part 8 (the left side of the page in FIG. 9), an objective lens part 8a disposed opposite the eye to be examined E is installed. Also, on the examiner's side of the main body part 8 (the right side of the page in FIG. 9), an objective lens part 8b for observing the fundus oculi of the eye to be examined E with the naked is installed.
Furthermore, connected to the main body part 8 is a still camera 9 for producing a still image of a fundus oculi of the eye to be examined E and an imaging device 10 such as a TV camera, etc. for producing still images or moving images of a fundus oculi. The still camera 9 and the imaging device 10 are formed removably with respect to the main body part 8.
As a still camera 9, in accordance with various conditions such as the purpose of an examination or the saving method of produced images, etc., a digital camera equipped with imaging elements such as CCD (Charge Coupled Device) or CMOS (Complementary Metal Oxide Semiconductor), a film camera, and an instant camera, etc. may interchangeably be used when it is appropriate. The main body part 8 is equipped with a mounting part 8c for interchangeably mounting such a still camera 9.
If the still camera 9 or the imaging device 10 is for taking digital images, the image data of the produced fundus image may be sent to a device such as a computer, etc. connected to the fundus camera 1000 and be observed as a fundus image by being displayed on the display. Also, the image data in an image storing device connected to the fundus camera 1000 can be sent to compile a database and be used as electronic data for creating medical charts, etc.
Furthermore, on the examiner's side of the main body part 8, a touch panel monitor 11 is installed. On this touch panel monitor 11, fundus images of the eye to be examined E created based on the picture signals output from the still camera 9 (a digital method thereof) or the imaging device 10 are displayed. Moreover, on the touch panel monitor 11, the xy coordinate system with the center of the screen as the origin is displayed overlapped with a fundus image. When the screen is touched by the examiner, the coordinate value corresponding to the touched position is displayed.
Next, referring to FIG. 10, a composition of an optical system of the fundus camera 1000 is described. The fundus camera 1000 is provided with an illuminating optical system 100 to light the fundus oculi Ef of an eye to be examined E, an imaging optical system 120 to guide the fundus reflection light of the illumination light to the eyepiece part 8b, a still camera 9, and an imaging device 10.
The illuminating optical system 100 comprises: an observation light source 101, a condenser lens 102, an imaging light source 103, a condenser lens 104, an exciter filter 105 and 106, a ring transparent plate 107, a mirror 108, a liquid crystal display (LCD) 109, an illumination diaphragm 110, a relay lens 111, an aperture mirror 112, and an objective lens 113.
The observation light source 101 consists of a halogen lamp, etc. and emits fixed light (continuous light) for observing the fundus. The condenser lens 102 is an optical element that converges the fixed light (observation illumination light) emitted by the observation light source 101 and substantially evenly irradiates the observation illumination light to the fundus oculi.
The imaging light source 103 consists of a xenon lamp, etc. to be flashed when producing fundus oculi Ef images. The condenser lens 104 is an optical element that converges the flash light (imaging illumination light) emitted by the imaging light source 103 and irradiates the fundus oculi Ef evenly with the imaging illumination light.
The exciter filters 105 and 106 are the filters to be used when fluorography of ocular fundus images of a fundus oculi Ef takes a place. The exciter filters 105 and 106 respectively can be inserted and/or removed on the optical path by a drive mechanism such as a solenoid, etc. The exciter filter 105 is disposed on the optical path in the event of FAG (fluorescein angiography). Whereas, the exciter filter 106 is disposed on the optical path in the event of ICG (indocyanine green angiography). Furthermore, when color images are being obtained, both exciter filters 105 and 106 are retracted from the optical path.
The ring transparent plate 107 is disposed in a conjugating location with a pupil of the eye to be examined E, and is equipped with a ring transparent part 107a taking an optical axis of the illuminating optical system 100 as a center. The mirror 108 reflects the illumination light emitted by the observation light source 101 or by the imaging light source 103 in the direction of the optical axis of the imaging optical system 120. The LCD 109 displays a fixation target (not illustrated) for fixing the eye to be examined E.
The illumination diaphragm 110 is a diaphragm member to shut out a part of the illumination light for flare prevention, etc. This illumination diaphragm 110 is composed movably in the light axial direction of the illuminating optical system 100, and is thus capable of changing the illuminating region of the fundus oculi Ef.
The aperture mirror 112 is an optical element to combine an optical axis of the illuminating optical system 100 and an optical axis of the imaging optical system 120. In the center region of the aperture mirror 112 an aperture part 112a is opened. The light axis of the illuminating optical system 100 and the light axis of the imaging optical system 120 are to be crossed at a substantially central location of this aperture part 112a. The objective lens 113 is installed in the objective lens part 8a of the main body part 8.
The illuminating optical system 100 having such a composition illuminates a fundus oculi Ef in the following manner. First, the observation illumination light is output when the observation light source 101 is lit during fundus observation. This observation illumination light irradiates the ring transparent plate 107 through the condenser lenses 102 and 104. (The exciter filters 105 and 106 are removed from the optical path.) The light passed through the ring transparent part 107a of the ring transparent plate 107 is reflected by the mirror 108 and is reflected along the optical axial direction of the imaging optical system 120 due to the aperture mirror 112 through the LCD 109, the illumination diaphragm 110 and the relay lens 111. The observing illumination light reflected by the aperture mirror 112 advances in the optical axial direction of the imaging optical system 120 and is converged by the objective lens 113, to be made incident onto the eye to be examined E, and illuminates the fundus oculi Ef.
Then, the ring transparent plate 107 is disposed in a conjugating location with the pupil of the eye to be examined E, and on the pupil a ring shaped image of the entering observation illumination light is formed. The fundus reflection light of the entered observation illumination light is to be emitted from the eye to be examined E through a central dark part of the ring image on the pupil. As described, it is to protect the effect of observing illumination light entering the eye to be examined E with respect to the fundus reflection light of the observing illumination light.
On the other hand, when imaging the fundus oculi Ef, flush light is emitted from the imaging light source 103 and the imaging illumination light is irradiated onto the fundus oculi Ef through the same path. In the event of photofluographing, either the exciter filter 105 or the exciter filter 106 is disposed selectively on the optical path depending on whether FAG imaging or ICG imaging is required.
Whereas, imaging optical system 120 comprises: an objective lens 113, an aperture mirror 112 (an aperture part 112a thereof), an imaging diaphragm 121, a barrier filter 122 and 123, a variable magnifying lens 124, a relay lens 125, an imaging lens 126, a quick return mirror 127 and an imaging media 9a. Herein, the imaging media 9a is an arbitrary imaging media (image pick-up elements such as CCD, camera film, instant film, etc.) used for a still camera 9.
The fundus reflection light of the illumination light, emitted through the central dark part of the ring shaped image formed on the pupil from the eye to be examined E, enters the imaging diaphragm 121 through the aperture part 112a of the aperture mirror 112. The aperture mirror 112 reflects cornea reflection light of the illumination light and acts so as not to mix the cornea reflection light into the fundus reflection light made incident onto the imaging diaphragm 121. As a result, the generation of flare on the observation images and/or produced images is prevented.
The imaging diaphragm 121 is a plate shaped member at which plural circular light transparent parts of different sizes are formed. The plural light transparent parts constitute different diaphragms with different diaphragm values (F value), and are to be disposed alternatively on the optical path by a drive mechanism (not illustrated herein).
The barrier filters 122 and 123 can be inserted and/or removed on the optical path by a drive mechanism such as a solenoid, etc. In the event of FAG imaging, the barrier filter 122 is disposed on the optical path while in the event of ICG imaging the barrier filter 123 is inserted onto the optical path. Furthermore, when producing color images the barrier filters 122 and 123 are to be retracted from the optical path.
The variable magnifying lens 124 is to be movable in the light axial direction of the imaging optical system 120 by a drive mechanism (not illustrated herein). This makes it possible to change the magnifying ratio of an observation and the magnifying ratio in imaging, and to focus images of a fundus oculi. The imaging lens 126 is a lens to form an image of the fundus reflection light from an eye to be examined E on the imaging media 9a. 
The quick return mirror 127 is disposed rotatably around a rotary shaft 127a by a drive mechanism not illustrated herein. In the event of imaging a fundus oculi Ef with the still camera 9, the fundus reflection light is supposed to be guided to the imaging media 9a by springing up the quick return mirror 127 that is obliquely mounted on the optical path. Whereas, in the event of imaging a fundus oculi with an imaging device 10 or of observing the fundus oculi with the naked eye of the examiner, the quick return mirror 127 is to be obliquely mounted on the optical path to upwardly reflect the fundus reflection light.
The imaging optical system 120 is further provided with a field lens (eye vision lens) 128 for guiding the fundus reflection light reflected by the quick return mirror 127, a switching mirror 129, an eyepiece 130, a relay lens 131, a reflection mirror 132, an imaging lens 133 and an image pick up element 10a. The image pick up element 10a is an image pick up element such as CCD, etc. installed internally in the imaging device 10. On the touch panel monitor 11 a fundus oculi image Ef' imaged by the image pick up element 10a is be displayed.
The switching mirror 129 is to be rotatable around the rotary shaft 129a as well as the quick return mirror 127. This switching mirror 129 is obliquely disposed on the optical path during observation with the naked eye and guides reflected light on the fundus oculi to the eyepiece 130.
Also, when a fundus image is formed by the imaging device 10, the switching mirror 129 is retracted from the optical path, and the fundus reflection light is guided toward an image pick-up element 10a. In this case, the fundus reflection light is directed toward a relay lens 131, is reflected by the mirror 132, and is formed on the image pick-up element 10a by the imaging lens 133.
Such a fundus camera 1000 is a fundus observation apparatus to be used for observing the state of the surface of a fundus oculi Ef, that is, the retina. In other words, a fundus camera 1000 is a fundus observation apparatus to obtain a 2-dimensional fundus oculi image when it sees the fundus oculi Ef from the corneal direction onto the eye to be examined E. On the other hand, in the deep layer of retina tissues such as where the choroidea or sclera exist, technology for observing these deep layer tissues has been desired, but, in recent years, devices for observing these deep layer tissues have been practically implemented (e.g. JP Patent laid-open No. 2003-00543, JP Patent laid-open No. 2005-241464).
The fundus observation apparatus disclosed in JP Patent laid-open No. 2003-00543 and JP Patent laid-open No. 2005-241464 are devices to which so called OCT (Optical Coherence Tomography) technology is applied. With such fundus observation devices, low coherence light is split into two, one of which (signal light) is guided to a fundus oculi and the other one (reference light) is guided to a given reference object, while at the same time this is a device to form tomographic images of the surface and the deep layer tissue of a fundus oculi, and to form the 3-dimensional image from the tomographic images, by detecting and analyzing the interference light obtained by overlaying the signal light that has passed through the fundus oculi and the reference light that has been reflected by the reference object. Such images are called light CT images or OCT images, etc.
In order to capture the state of a fundus oculi (presence/absence of a disease or the progressing state, the degree of a therapy effect or a recovery state, etc.) in detail, it is desirable to consider both the state of fundus surface (retina) and the state of deep layer tissues (choroidea or sclera). However, by just observing an image .of the fundus surface obtained from a fundus camera, it is difficult to capture the state of the deep layer tissues in detail, while, with tomographic images of the fundus oculi obtained from an optical image measuring device, it was difficult to capture the detailed state of the fundus surface or the entire retina.
Furthermore, in order to determine the state of fundus oculi comprehensively, it is considered to be desirable to determine the state of a disease by taking both the state of the retina and the state of deep layer tissues into consideration. That is, in order to improve the accuracy in determining the condition of a disease, etc., it is desirable to refer to more information and also to refer to information from multiple angles.
For this purpose, it is desirable to use a fundus observation device which permits to obtain both a fundus image from a fundus camera and a fundus image from an optical image measuring device. In particular, if it is possible to simultaneously produce both images, it permits to observe the condition of the fundus by another fundus image in imaging one fundus image.
However, with conventional fundus observation devices, it was difficult to capture both a 2-dimensional surface image of the fundus of an eye to be examined by a fundus camera, a tomographic image of the fundus, and a 3-dimensional image by an optical image measuring device. In particular, it was difficult to capture both fundus images at the same time.
Also, to form a fundus observing device for capturing both a fundus image by a fundus camera and a fundus image by an optical image measuring device, it is desirable to irradiate the signal light through the optical system of a fundus camera to the fundus and to overlap with the reference light by guiding the signal light directed toward the fundus. That is, by guiding the signal light by the optical system of a fundus camera, the tomographic images of the same position on the fundus oculi as the image by a fundus camera can be captured and the condition of the position on the fundus oculi can be observed in detail.
However, when a composition is adapted in which the signal light is guided by the optical system of a fundus camera, the signal light passes through more optical elements than a conventional optical image measuring device. Thus, due to the effect of the dispersion of these optical elements, the interference efficiency of the signal light and the reference light decreases such that sufficient intensity interference light may not be generated. Therefore, when the image is formed based on the deficient intensity interference light, the OCT image is of low contrast and is unclear, as with a conventional optical image measuring device.
Furthermore, with conventional optical image measuring devices, the difference in the effect between both the signal light and the reference light is compensated by the image processing. But for both fundus images by a fundus camera and fundus images by an optical image measuring device of an adequate fundus observing device, there is a large difference between the number of optical elements passing through the signal light and the number of optical elements passing through the reference light such that there is a difference between the effect of dispersion to the signal light and the effect of dispersion to the reference light, and correction by the image processing may be insufficient.
The present invention is intended to solve such problems by capturing both the image of the surface of the fundus oculi and the tomographic images of the fundus oculi, and it particularly intends to provide a fundus observation device capable of simultaneously capturing both of these fundus images.
Further, the present invention can capture both the image of the surface of the fundus oculi and the tomographic images of the fundus oculi, with a further purpose of providing a fundus observing device capable of controlling the decrease in interference efficiency of both the signal light and the reference light by optical image measurement.